Mana Eggs can be found on the field. You can trade them at a local store for a magic element in return. Here are the locations of all Mana Eggs.

1. Ghost Ship, obtained after defeating Squid King (boss).
2. Merryl Road, on the west side.
3. New Palm, road under the church. It's hard to find, just get all the water out of there.
4. Rangle Montains, located somewhere west.
5. Rangle Montains, left side of the exit.
6. Dom Ruins, in a chest near the boss.
7. Valley of the Flying Dragon, Where the plant forms a going-around-stairs.
8. Valley of the Flying Dragon, near the exit, hidden near a turning flower.
9. Mount Typhoon, on an island surrounded with poison.
10. Typhoon Tower, left hall from the entrance.
11. Petrified Forest, keep going left after entering the petrified Cafu Village.
12. Alent, near the entrance at the stone pillars.
13. Gaia, you can earn it by defeating some enemies, but the eggs are useless at that point, since you can't go back to a store.